This invention relates to down hole drilling and or production apparatus and particularly relates to a circulation tool.
It is considered desirable in the art of drilling for oil or gas to be able to circulate drilling fluid at all material times down a drill string. The present invention recognises the need for a sub or tool connectable in a drill string or the like that may be used for maintaining and or reinstating circulation, notwithstanding the operation of other tools or processes.
For example, in our co-pending International Patent Application Number PCT/GB98/03795 there is described an inner string suspended from a drill pipe which prevents circulation. At the bottom of the drill string is a sub with a generally open port to enable circulation thereat.
It is an object of the present invention to provide a sub or tool of suitable design for use in such an application.
Similarly, a tool or sub for enabling or manipulating circulation may be required for use over a mud motor or the like.
A further object of the invention is to provide a tool having suitability for use in well-bore cleanup operations, including the cleaning of risers.
A yet further object of the present invention is to meet the aforementioned objections while providing for circulation via radial and axial outlets in a tool or sub.